On Tuesday, the NHS National Emergency Pressures Panel took the drastic step of urging health trusts to delay non-urgent operations until at least the end of the month. Officials said up to 55,000 operations could be deferred.

Speaking during a visit to Frimley Park Hospital in Surrey, the Prime Minister said: "I know it's difficult, I know it's frustrating, I know it's disappointing for people and I apologise."

"I recognise that it's difficult for people who are facing delays, I recognise it's difficult if somebody is delayed on their admission to hospital or if somebody has an operation postponed. We hope to ensure that those operations can be reinstated as soon as possible."

However, the Prime Minister claimed the winter crisis had been prepared for "better than ever before."

She said: "The NHS was better prepared for this winter than ever before. We have put extra resources in — £437 million extra — but of course its the staff who make the difference. It's their dedication and hard work that ensures that people are getting the treatment they need."

Measures have been put in place to ensure people needing urgent care receive it, she said.

Ms May added: "We are putting record amounts of money into the NHS. We recognise that we wanted to ensure plans were there for the winter pressures — that's why we put £437 million extra into the NHS over this particular period. Record levels of funding are going into the National Health Service.

"There are pressures over the winter period but these have been planned for better than ever before."

Ms May refused to echo her Health Secretary, Jeremy Hunt, in describing the situation as a crisis.

It comes as new data revealed there were fewer NHS beds available over Christmas than there were last year, despite Ms May having claimed yesterday that "there are more beds available across the system".

Average bed occupancy across all trusts jumped to 91.7% between Christmas Day and New Year's Eve compared to 90% occupancy in the same week last year, analysis by The Independent's analysis showed.

It remains significantly higher than the recommended safe operating levels of 85% occupancy, above which hospital infections and "bed crises" become more common.